Fuel tank caps are used to close the end of the fuel filler neck between occasions when a vehicle is refueled. Fuel tank caps include a pressure relief valve that is calibrated to prevent build-up of pressure in the fuel tank. Fuel tank caps are also designed to maintain the seal below a certain pressure to preclude leakage.
Recent regulations and regulatory test requirements have been established which have the objective of minimizing release of unburned hydrocarbons from mobile sources, such as vehicles. To meet these regulatory requirements, it has been suggested that onboard diagnostic leak detection hardware be provided on vehicles. Onboard diagnostic leak detection hardware is complex and expensive and can increase the cost of a motor vehicle without any corresponding benefit in the performance of a vehicle.
One approach to providing control of liquid/vapor discharge out of the fuel filler neck if the closure cap is either left off or not fully secured is disclosed in U.S. Pat. No. 5,320,147, which is assigned to the assignee of this application. U.S. Pat. No. 5,320,147, which issued to Jamrog, includes a module containing two one-way valves acting in opposite directions to provide vacuum-break and pressure relief, independent of the pressure relief valve in the fuel tank cap. The Jamrog system, while effective, requires considerable calibration of the valves. The complexity of the Jamrog system also adds to the cost of the vehicle.
Another disadvantage of some prior art fuel tank cap and retainer combinations is they are not user friendly, and require some dexterity and strength to properly install. To meet consumer demand for ease of operation, quick install fuel caps have been developed that are easy to install and are less likely to be improperly installed by a consumer.